1,721,017 research outputs found
Carbonate-to-biosilica transition at the Norian–Rhaetian boundary controlled by rift-related subsidence in the western Tethyan Lagonegro Basin (southern Italy)
Full text linkReceived 20 December 2015
Received in revised form 26 April 2016 Accepted 5 May 2016
Available online 8 May 2016
Keywords:
Elemental geochemistry Rare earth elements Chemical index of alteration Redox conditions
UPPER Triassic
1. Introduction
The breakup of the supercontinent Pangea started with rifting in modern eastern North America (Schlische et al., 2003), southern Iberia (Martin-Rojas et al., 2009), and western Morocco and the Atlas Moun- tains region in northwestern Africa (Dewey et al., 1973; Le Roy and Piqué, 2001; Schettino and Turco, 2009, 2011). In the western Tethyan region, this event was marked by the opening of multiple rift basins comprising the Ionian Ocean (Fig. 1). The kinematics of this rifting event resulted in the formation of a number of independent microplates (including the microplate called Adria) and pull-apart basins between Africa and Eurasia (Schettino and Turco, 2011). This first phase of rifting in the Ionian Ocean terminated at the Triassic/Jurassic boundary, when
⁎ Correspondingauthor.
⁎⁎ Correspondence to: T.J. Algeo, Department of Geology, University of Cincinnati,
Cincinnati, OH 45221-0013, USA.
E-mail addresses: [email protected] (M. Casacci), [email protected]
(T.J. Algeo).
http://dx.doi.org/10.1016/j.palaeo.2016.05.007
0031-0182/© 2016 Elsevier B.V. All rights reserved.
abstract
The Lagonegro Basin, located in the Southern Apennines, Italy, records a transition from carbonate sediments of the Calcari con Selce Fm. (“Cherty Limestone”) to biosiliceous sediments of the Scisti Silicei Fm. (“Siliceous Shale”) around the Norian–Rhaetian boundary (NRB), Upper Triassic. Sedimentologic and chemostratigraphic analysis of three sections (Pignola-Abriola, Monte Volturino, and Madonna del Sirino) representing a proximal-to-distal transect across the basin document marine productivity, redox, and chemical weathering con- ditions. The basin was characterized by low to moderate productivity and mainly oxic deep waters, with no sys- tematic secular variation throughout the ~ 10-Myr-long study interval. A weathering proxy, the chemical index of alteration (CIA*), shifts toward higher values (from ~0.70 to ~0.80) in all three study sections, suggesting devel- opment of warmer and/or more humid conditions just before the NRB. The lack of evidence for changes in marine productivity or redox conditions and the time-transgressive nature of the carbonate-biosilica transition suggests that the latter was caused not by changes in planktonic communities but, rather, by a rise in the CCD, the most likely cause of which was seafloor subsidence within the actively rifting Ionian Ocean (i.e., the westernmost branch of the Tethys Ocean). The tectonically active character of the Lagonegro Basin is also reflected in evidence of synsedimentary paleoseismic activity, e.g., numerous debris flows around the basin margins. The present study thus documents sedimentologic changes within a marginal basin in a geologically young ocean
Paleoceanographic changes in the Lagonegro Basin (southern Italy) during the Late Triassic linked to oceanic rifting in the western Tethyan region
No full textOceanic rift-driven transition from carbonate to biosilica sedimentation in the western Tethyan Lagonegro Basin (southern Italy) during the Late Triassic
No full textNorian/Rhaetian radiolarian assemblages related to paleoenvironmental conditions of the Lagonegro Basin (southern Apennines, Italy)
No full textThe Upper Triassic Monte Volturino section (Lagonegro Basin, Southern Italy): Evidence for felsic volcanic activity in the western Tethyan realm
No full textNew biostratigraphical constraints for the Norian/Rhaetian boundary: data from Lagonegro Basin, Southern Apennines, Italy
Full text linkFour stratigraphic sections belonging to Lagonegro succession (Southern Apennines) at Mt S. Enoc, Pignola-Abriola, Sasso di Castalda and Mt Volturino have been studied in detail under to provide a new micro-palaeontological data set based on conodonts and radiolarians for the characterization of the Norian⁄Rhaetian interval. The studied sec- tions represent the different settings of the Lagonegro Basin (from proximal to distal facies) and permit a detailed, integrated, biostratigraphy of the Calcari con Selce (cherty limestones) and Scisti Silicei formations (bedded cherts with radiolarians) to be drawn up. The upper portion of the Calcari con Selce Formation, exhibits intermediate charac- teristics between the Calcari con Selce and Scisti Silicei Formation, in particular the pro- gressive decrease in carbonate content against an increase in shales and cherts. Within the four sections studied, the Norian ⁄ Rhaetian interval has been documented both with conodonts and radiolarians. Because of the continuity and the absence of condensed facies, it has been possible to recognize the morphocline between species Misikella hern- steini and Misikella posthernsteini, here represented by all the transitional forms charac- terized by common features between the two species, gathered in three evolutionary steps. Moreover, the morphocline between M. hernsteini and M. posthernsteini has been involved in the definition of the Norian ⁄ Rhaetian Boundary, recognizing thus the FAD of M. posthernsteini, one of the possible biomarkers proposed for the boundary. The rich, well-preserved, radiolarian associations of Pignola-Abriola, Sasso di Castalda and Mt Volturino permit the correlation of Tethyan and American conodont successions, high- lighting the importance of the mostly coincident occurrences of M. posthernsteini and Epigondolella mosheri morphotype A, which correspond to the base of Proparvicingula moniliformis A. Z. and the disappearance of bivalve Monotis. These coincident bioevents are used here to define the base of the Rhaetian stage
I miliari di Valentiniano II, Teodosio e Arcadio della Venetia: una proposta di seriazione
No full textAnalisi di una serie di quattro miliari di Valentiniano II, Teodosio e Arcadio rinvenuti nella Venetia, confrontati con i miliari degli stessi imperatori noti nel resto d'Italia, al fine di affrontare il tema del significato e della committenza di tali materiali
Città e terriotorio: un rapporto complesso
No full textRassegna delle problematiche che presenta, nel mondo antico, il rapporto fra una città e il territorio ad essa afferente
Il praefectus arcis nella documentazione di età romana, in E. Todisco, M. Traverso, Misurare il tempo. Riflessi dell'antico nelle iscrizioni latine moderne: il caso del praefectus arcis, pp. 545-560
No full text- …
